package cz.tomasdvorak.cars.utils;

import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.net.URISyntaxException;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;

/**
 * Tool for finding java classes in the file system.
 * @author tdvorak
 */
public class ClassExplorer {
    /**
     * Scans all classes accessible from the context class loader which belong to the given package and subpackages.
     *
     * @param packageName The base package
     * @return Array of found classes
     * @throws ClassNotFoundException
     * @throws IOException
     */
    public static Class[] getClasses(String packageName)
            throws ClassNotFoundException, IOException, URISyntaxException {
        ClassLoader classLoader =
                Thread.currentThread().getContextClassLoader();
        assert classLoader != null;
        String path = packageName.replace('.', '/');
        Enumeration<URL> resources = classLoader.getResources(path);
        List<File> dirs = Lists.arrayList();
        while (resources.hasMoreElements()) {
            URL resource = resources.nextElement();
            dirs.add(new File(resource.toURI()));
        }
        ArrayList<Class> classes = Lists.arrayList();
        for (File directory : dirs) {
            classes.addAll(findClasses(directory, packageName));
        }
        return classes.toArray(new Class[classes.size()]);
    }

    /**
     * Recursive method used to find all classes in a given directory and subdirs.
     *
     * @param directory   The base directory
     * @param packageName The package name for classes found inside the base directory
     * @return List of classes found in package under directory
     * @throws ClassNotFoundException
     */
    private static List<Class> findClasses(File directory, String packageName)
            throws ClassNotFoundException {
        List<Class> classes = Lists.arrayList();
        if (!directory.exists()) {
            return classes;
        }
        File[] files = directory.listFiles();
        for (File file : files) {
            if (file.isDirectory()) {
                assert !file.getName().contains(".");
                classes.addAll(findClasses(file, packageName + "." + file.getName()));
            } else if (file.getName().endsWith(".class")) {
                classes.add(Class.forName(packageName + '.' + file.getName()
                        .substring(0, file.getName().length() - 6)));
            }
        }
        return classes;
    }

}